1. Field of the Invention
The present invention relates to a method for charging anode(s) into a furnace in smelting processes for copper concentrates, and relates to a method for designing a furnace.
2. Description of the Related Art
An example of a known conventional smelting process (Mitsubishi continuous copper smelting and converting process (Mitsubishi process)) for copper concentrates consists of performing smelting treatment continuously by connecting a smelting furnace (S furnace), a slag cleaning furnace (CL furnace) and a converting furnace (C furnace) by means of launders. In this process, copper concentrates are melted in the smelting furnace to form a matte having as its main components copper sulfide and iron sulfide, and a slag having as its main components fluxes, iron oxide, gangue of raw materials, and so forth. Next, the matte and slag are separated in the slag cleaning furnace, and then crude copper is produced by oxidizing the matte in the converting furnace. The crude copper (melt) obtained in this manner is then put in an anode furnace where oxidation and reduction are caused to occur to improve the grade of the copper. Moreover, this melt is then cast into anodes which have approximately rectangular parallelopiped shapes, and the anodes are inserted into electrolytic cells where electrolytic refining is carried out to produce electrolytic copper.
When electrolytic refining is carried out, the anodes dissolve in the electrolyte, and the thickness of the anodes gradually decreases, resulting in a thin plate shape. In this case, since there is a risk that the anodes may be fall into the electrolytic cells if they become excessively thin, electrolytic refining is terminated and the anodes are recovered when they have reached a certain thickness. Each thin plate shaped anode obtained at this time (to be referred to as a xe2x80x9cspent anodexe2x80x9d, weight: 50-110 kg) is returned to the copper smelting process and is again melted in the furnace. When the spent anode is charged into the furnace, the spent anode is preferably charged into the converting furnace which has surplus heat since heat for melting the spent anode is required. However, if the spent anode is charged directly into the converting furnace, the spent anode may impact the furnace bottom, resulting in a risk of damage to the furnace bottom. In contrast, as disclosed in U.S. Pat. No. 5,685,892, a method is proposed in which the spent anode is charged into the converting furnace after slightly bending the anode at the end of the charging direction. According to this method, the spent anode can be charged into the converting furnace without the risk of damage.
However, some anodes used in the electrolytic refining are taken out of the electrolytic cell before completely finishing the electrolytic refining, and they are thicker and heavier than the above-mentioned spent anodes (to be referred to as spent anodes in the broad sense). With respect to these spent anodes in the broad sense and anodes for which the weight and shape during casting are not standard (to be referred to as xe2x80x9creject anodesxe2x80x9d), there is the problem of being unable to avoid these anodes colliding with the furnace bottom of the converting furnace simply by bending their ends and charging directly into the converting furnace as described above.
Although these anodes having a weight of 110 kg or more have been charged into the anode furnace, since the heat of the anode furnace is inadequate, a large amount of heat is required to melt these anodes. Consequently, a large amount of fuel is required to heat the anode furnace, which ends up resulting in the problem of high cost. In addition, since it is necessary to change the furnace in which the anodes are charged according to the weight of the anodes, there was also the problem of a large work burden.
In consideration of the above circumstances, objects of the present invention are to provide a method for charging anode(s) into a furnace, and to provide a method for designing a furnace that allows even the above spent anodes in the broad sense and reject anodes to be charged into the furnace without damaging the furnace bottom.
A first aspect according to the present invention for solving the above problems is characterized by providing a method for charging anode(s) comprising: bending anode(s) having a roughly rectangular plate shape at the end of its charging direction, and charging the anode into a melt stored in a furnace through a slope; wherein, when the depth of the melt is taken to be D (cm), the height of the slope is taken to be H (cm), the inclination angle of the slope is taken to be xcex2 (xc2x0) and the thickness of the anode is taken to be b (cm), the bending angle xcex1 (xc2x0) of the anode and the length c (cm) of the bent end of the anode are set to satisfy the following relationship:
Equation (1): D greater than Axc3x97(c sin xcex1/b)B+0.06(H-190); provided that A and B are given by: 
Equation (2):A=xe2x88x921051(sin xcex2)2+2028 sin xcex2xe2x88x92839.3, and 
Equation (3):B=7.378(sin xcex2)2xe2x88x9211.64 sin xcex2+3.806. 
When composed in the manner described above, by calculating the bending angle xcex1 of the anode and length c of the bent end according to the above equations (1) through (3), collision of the anode charged into the furnace with the furnace bottom can be prevented. Thus, there is no risk of the furnace bottom being damaged by the charging of anode(s). In addition, since the above equations (1) through (3) can not only be applied to the above-mentioned spent anodes (weight: 50-110 kg), but also to spent anodes in the broad sense and to reject anodes (weight: 110 kg or more) that are heavier than the spent anodes, it is no longer necessary to change the type of furnace in which the anodes are charged according to the weight of the anodes, thereby making it possible to simplify the process.
A second aspect according to the present invention is characterized in that the furnace in which the anodes are charged is the converting furnace. That is, when the anode furnace is used for melting the charged anodes, a large amount of heat for heating and melting the anode in the anode furnace is required. On the other hand, when using the converting furnace, since exothermic reactions take place in the furnace and generating surplus heat, fuel for heating and melting the charged anode is not required. As a result, since all of the heat required for heating and melting the anode is provided by the surplus heat of the converting furnace, the thermal balance of the process can be significantly improved. In addition, since the anode can function as a coolant which maintains the converting furnace at the proper temperature, the coolant which is conventionally used is no longer required. Thus, in addition to being able to reduce costs considerably, energy efficiency can also be improved.
A third aspect according to the present invention is characterized in that the inclination angle of the slope is 50-70xc2x0. When composed in this manner, whether or not the anode will collide with the furnace bottom can be determined with extremely high accuracy from the above-mentioned equations (1) through (3).
A fourth aspect according to the present invention is characterized in that the anode is charged by an anode charging apparatus equipped with an opening provided on the ceiling or wall of a converting furnace in the smelting process for copper concentrates that connects the inside and outside of the converting furnace, an outer shutter and an inner shutter attached at a distance from the converting furnace in the inside and outside directions of the converting furnace that respectively and independently open and close the opening, and a charging mechanism that charges the anode into the opening.
When composed in the above manner, after lowering the anode into the opening with the charging mechanism in the state in which the outer shutter is open and the inner shutter is closed, the anode is temporarily stopped by engaging with a receiving mechanism arranged between both shutters. Next, the anode is charged into the converting furnace by opening the inner shutter after closing the outer shutter. Since the anode charging can be carried out with the inside and outside of the converting furnace isolated, the converting furnace can be stable thermally without heat loss and gas emission. In addition, the height H of the slope can be adjusted to the optimum value by adjusting the position of the receiving mechanism, thereby being able to effectively prevent the anode from colliding with the furnace bottom.
A fifth aspect according to the present invention is characterized by a method for designing furnace which has a slope for charging anode(s) having roughly a rectangular shape, and its end is bent, into a melt stored in the furnace; wherein, when the bending angle of the anode is taken to be xcex1 (xc2x0),the length of the bent end of the anode is taken to be c (cm), the thickness of the anode is taken to be b (cm) and the inclination angle of the slope is taken to be xcex2 (xc2x0), the depth D (cm) of the melt and the height H (cm) of the slope are set to satisfy the following relationship:
Equation (1):D greater than Axc3x97(c sin xcex1/b)B+0.06(H-190); provided that A and B are given by: 
Equation (2):A=xe2x88x921051(sin xcex2)2+2028 sin xcex2xe2x88x92839.3, and 
Equation (3):B=7.378(sin xcex2)2xe2x88x9211.64 sin xcex2+3.806. 
When composed in the above manner, the anode charged into the furnace can be prevented from colliding with the furnace bottom by calculating the depth D (cm) of the melt and the height H (cm) of the slope according to the above equations (1) through (3). Thus, there is no risk of the furnace bottom being damaged when the anode is charged thereinto. In addition, since the above equations (1) through (3) can not only be applied to the spent anodes, but also to the spent anodes in the broad sense and to reject anodes, there is no need to change the kind of furnace in which the anodes are charged according to the anode weight, thereby making it possible to simplify the process.